diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/bcachefs/errorcodes.rst | 30 | ||||
| -rw-r--r-- | Documentation/filesystems/f2fs.rst | 54 | ||||
| -rw-r--r-- | Documentation/filesystems/files.rst | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/fscrypt.rst | 27 | ||||
| -rw-r--r-- | Documentation/filesystems/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/filesystems/locking.rst | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/ntfs.rst | 466 | ||||
| -rw-r--r-- | Documentation/filesystems/overlayfs.rst | 16 | ||||
| -rw-r--r-- | Documentation/filesystems/proc.rst | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.rst | 16 | ||||
| -rw-r--r-- | Documentation/filesystems/xfs/xfs-online-fsck-design.rst | 30 |
11 files changed, 106 insertions, 542 deletions
diff --git a/Documentation/filesystems/bcachefs/errorcodes.rst b/Documentation/filesystems/bcachefs/errorcodes.rst new file mode 100644 index 000000000000..2cccaa0ba7cd --- /dev/null +++ b/Documentation/filesystems/bcachefs/errorcodes.rst @@ -0,0 +1,30 @@ +.. SPDX-License-Identifier: GPL-2.0 + +bcachefs private error codes +---------------------------- + +In bcachefs, as a hard rule we do not throw or directly use standard error +codes (-EINVAL, -EBUSY, etc.). Instead, we define private error codes as needed +in fs/bcachefs/errcode.h. + +This gives us much better error messages and makes debugging much easier. Any +direct uses of standard error codes you see in the source code are simply old +code that has yet to be converted - feel free to clean it up! + +Private error codes may subtype another error code, this allows for grouping of +related errors that should be handled similarly (e.g. transaction restart +errors), as well as specifying which standard error code should be returned at +the bcachefs module boundary. + +At the module boundary, we use bch2_err_class() to convert to a standard error +code; this also emits a trace event so that the original error code be +recovered even if it wasn't logged. + +Do not reuse error codes! Generally speaking, a private error code should only +be thrown in one place. That means that when we see it in a log message we can +see, unambiguously, exactly which file and line number it was returned from. + +Try to give error codes names that are as reasonably descriptive of the error +as possible. Frequently, the error will be logged at a place far removed from +where the error was generated; good names for error codes mean much more +descriptive and useful error messages. diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst index d32c6209685d..efc3493fd6f8 100644 --- a/Documentation/filesystems/f2fs.rst +++ b/Documentation/filesystems/f2fs.rst @@ -126,9 +126,7 @@ norecovery Disable the roll-forward recovery routine, mounted read- discard/nodiscard Enable/disable real-time discard in f2fs, if discard is enabled, f2fs will issue discard/TRIM commands when a segment is cleaned. -no_heap Disable heap-style segment allocation which finds free - segments for data from the beginning of main area, while - for node from the end of main area. +heap/no_heap Deprecated. nouser_xattr Disable Extended User Attributes. Note: xattr is enabled by default if CONFIG_F2FS_FS_XATTR is selected. noacl Disable POSIX Access Control List. Note: acl is enabled @@ -184,29 +182,31 @@ fault_type=%d Support configuring fault injection type, should be enabled with fault_injection option, fault type value is shown below, it supports single or combined type. - =================== =========== - Type_Name Type_Value - =================== =========== - FAULT_KMALLOC 0x000000001 - FAULT_KVMALLOC 0x000000002 - FAULT_PAGE_ALLOC 0x000000004 - FAULT_PAGE_GET 0x000000008 - FAULT_ALLOC_BIO 0x000000010 (obsolete) - FAULT_ALLOC_NID 0x000000020 - FAULT_ORPHAN 0x000000040 - FAULT_BLOCK 0x000000080 - FAULT_DIR_DEPTH 0x000000100 - FAULT_EVICT_INODE 0x000000200 - FAULT_TRUNCATE 0x000000400 - FAULT_READ_IO 0x000000800 - FAULT_CHECKPOINT 0x000001000 - FAULT_DISCARD 0x000002000 - FAULT_WRITE_IO 0x000004000 - FAULT_SLAB_ALLOC 0x000008000 - FAULT_DQUOT_INIT 0x000010000 - FAULT_LOCK_OP 0x000020000 - FAULT_BLKADDR 0x000040000 - =================== =========== + =========================== =========== + Type_Name Type_Value + =========================== =========== + FAULT_KMALLOC 0x000000001 + FAULT_KVMALLOC 0x000000002 + FAULT_PAGE_ALLOC 0x000000004 + FAULT_PAGE_GET 0x000000008 + FAULT_ALLOC_BIO 0x000000010 (obsolete) + FAULT_ALLOC_NID 0x000000020 + FAULT_ORPHAN 0x000000040 + FAULT_BLOCK 0x000000080 + FAULT_DIR_DEPTH 0x000000100 + FAULT_EVICT_INODE 0x000000200 + FAULT_TRUNCATE 0x000000400 + FAULT_READ_IO 0x000000800 + FAULT_CHECKPOINT 0x000001000 + FAULT_DISCARD 0x000002000 + FAULT_WRITE_IO 0x000004000 + FAULT_SLAB_ALLOC 0x000008000 + FAULT_DQUOT_INIT 0x000010000 + FAULT_LOCK_OP 0x000020000 + FAULT_BLKADDR_VALIDITY 0x000040000 + FAULT_BLKADDR_CONSISTENCE 0x000080000 + FAULT_NO_SEGMENT 0x000100000 + =========================== =========== mode=%s Control block allocation mode which supports "adaptive" and "lfs". In "lfs" mode, there should be no random writes towards main area. @@ -228,8 +228,6 @@ mode=%s Control block allocation mode which supports "adaptive" option for more randomness. Please, use these options for your experiments and we strongly recommend to re-format the filesystem after using these options. -io_bits=%u Set the bit size of write IO requests. It should be set - with "mode=lfs". usrquota Enable plain user disk quota accounting. grpquota Enable plain group disk quota accounting. prjquota Enable plain project quota accounting. diff --git a/Documentation/filesystems/files.rst b/Documentation/filesystems/files.rst index 9e38e4c221ca..eb770f891b27 100644 --- a/Documentation/filesystems/files.rst +++ b/Documentation/filesystems/files.rst @@ -116,7 +116,7 @@ before and after the reference count increment. This pattern can be seen in get_file_rcu() and __files_get_rcu(). In addition, it isn't possible to access or check fields in struct file -without first aqcuiring a reference on it under rcu lookup. Not doing +without first acquiring a reference on it under rcu lookup. Not doing that was always very dodgy and it was only usable for non-pointer data in struct file. With SLAB_TYPESAFE_BY_RCU it is necessary that callers either first acquire a reference or they must hold the files_lock of the diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst index e86b886b64d0..04eaab01314b 100644 --- a/Documentation/filesystems/fscrypt.rst +++ b/Documentation/filesystems/fscrypt.rst @@ -338,11 +338,14 @@ Supported modes Currently, the following pairs of encryption modes are supported: -- AES-256-XTS for contents and AES-256-CTS-CBC for filenames +- AES-256-XTS for contents and AES-256-CBC-CTS for filenames - AES-256-XTS for contents and AES-256-HCTR2 for filenames - Adiantum for both contents and filenames -- AES-128-CBC-ESSIV for contents and AES-128-CTS-CBC for filenames -- SM4-XTS for contents and SM4-CTS-CBC for filenames +- AES-128-CBC-ESSIV for contents and AES-128-CBC-CTS for filenames +- SM4-XTS for contents and SM4-CBC-CTS for filenames + +Note: in the API, "CBC" means CBC-ESSIV, and "CTS" means CBC-CTS. +So, for example, FSCRYPT_MODE_AES_256_CTS means AES-256-CBC-CTS. Authenticated encryption modes are not currently supported because of the difficulty of dealing with ciphertext expansion. Therefore, @@ -351,11 +354,11 @@ contents encryption uses a block cipher in `XTS mode `CBC-ESSIV mode <https://en.wikipedia.org/wiki/Disk_encryption_theory#Encrypted_salt-sector_initialization_vector_(ESSIV)>`_, or a wide-block cipher. Filenames encryption uses a -block cipher in `CTS-CBC mode +block cipher in `CBC-CTS mode <https://en.wikipedia.org/wiki/Ciphertext_stealing>`_ or a wide-block cipher. -The (AES-256-XTS, AES-256-CTS-CBC) pair is the recommended default. +The (AES-256-XTS, AES-256-CBC-CTS) pair is the recommended default. It is also the only option that is *guaranteed* to always be supported if the kernel supports fscrypt at all; see `Kernel config options`_. @@ -364,7 +367,7 @@ upgrades the filenames encryption to use a wide-block cipher. (A *wide-block cipher*, also called a tweakable super-pseudorandom permutation, has the property that changing one bit scrambles the entire result.) As described in `Filenames encryption`_, a wide-block -cipher is the ideal mode for the problem domain, though CTS-CBC is the +cipher is the ideal mode for the problem domain, though CBC-CTS is the "least bad" choice among the alternatives. For more information about HCTR2, see `the HCTR2 paper <https://eprint.iacr.org/2021/1441.pdf>`_. @@ -375,13 +378,13 @@ the work is done by XChaCha12, which is much faster than AES when AES acceleration is unavailable. For more information about Adiantum, see `the Adiantum paper <https://eprint.iacr.org/2018/720.pdf>`_. -The (AES-128-CBC-ESSIV, AES-128-CTS-CBC) pair exists only to support +The (AES-128-CBC-ESSIV, AES-128-CBC-CTS) pair exists only to support systems whose only form of AES acceleration is an off-CPU crypto accelerator such as CAAM or CESA that does not support XTS. The remaining mode pairs are the "national pride ciphers": -- (SM4-XTS, SM4-CTS-CBC) +- (SM4-XTS, SM4-CBC-CTS) Generally speaking, these ciphers aren't "bad" per se, but they receive limited security review compared to the usual choices such as @@ -393,7 +396,7 @@ Kernel config options Enabling fscrypt support (CONFIG_FS_ENCRYPTION) automatically pulls in only the basic support from the crypto API needed to use AES-256-XTS -and AES-256-CTS-CBC encryption. For optimal performance, it is +and AES-256-CBC-CTS encryption. For optimal performance, it is strongly recommended to also enable any available platform-specific kconfig options that provide acceleration for the algorithm(s) you wish to use. Support for any "non-default" encryption modes typically @@ -407,7 +410,7 @@ kernel crypto API (see `Inline encryption support`_); in that case, the file contents mode doesn't need to supported in the kernel crypto API, but the filenames mode still does. -- AES-256-XTS and AES-256-CTS-CBC +- AES-256-XTS and AES-256-CBC-CTS - Recommended: - arm64: CONFIG_CRYPTO_AES_ARM64_CE_BLK - x86: CONFIG_CRYPTO_AES_NI_INTEL @@ -433,7 +436,7 @@ API, but the filenames mode still does. - x86: CONFIG_CRYPTO_NHPOLY1305_SSE2 - x86: CONFIG_CRYPTO_NHPOLY1305_AVX2 -- AES-128-CBC-ESSIV and AES-128-CTS-CBC: +- AES-128-CBC-ESSIV and AES-128-CBC-CTS: - Mandatory: - CONFIG_CRYPTO_ESSIV - CONFIG_CRYPTO_SHA256 or another SHA-256 implementation @@ -521,7 +524,7 @@ alternatively has the file's nonce (for `DIRECT_KEY policies`_) or inode number (for `IV_INO_LBLK_64 policies`_) included in the IVs. Thus, IV reuse is limited to within a single directory. -With CTS-CBC, the IV reuse means that when the plaintext filenames share a +With CBC-CTS, the IV reuse means that when the plaintext filenames share a common prefix at least as long as the cipher block size (16 bytes for AES), the corresponding encrypted filenames will also share a common prefix. This is undesirable. Adiantum and HCTR2 do not have this weakness, as they are diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst index e18bc5ae3b35..0ea1e44fa028 100644 --- a/Documentation/filesystems/index.rst +++ b/Documentation/filesystems/index.rst @@ -98,7 +98,6 @@ Documentation for filesystem implementations. isofs nilfs2 nfs/index - ntfs ntfs3 ocfs2 ocfs2-online-filecheck diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index d5bf4b6b7509..e664061ed55d 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -29,7 +29,7 @@ prototypes:: char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen); struct vfsmount *(*d_automount)(struct path *path); int (*d_manage)(const struct path *, bool); - struct dentry *(*d_real)(struct dentry *, const struct inode *); + struct dentry *(*d_real)(struct dentry *, enum d_real_type type); locking rules: diff --git a/Documentation/filesystems/ntfs.rst b/Documentation/filesystems/ntfs.rst deleted file mode 100644 index 5bb093a26485..000000000000 --- a/Documentation/filesystems/ntfs.rst +++ /dev/null @@ -1,466 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -================================ -The Linux NTFS filesystem driver -================================ - - -.. Table of contents - - - Overview - - Web site - - Features - - Supported mount options - - Known bugs and (mis-)features - - Using NTFS volume and stripe sets - - The Device-Mapper driver - - The Software RAID / MD driver - - Limitations when using the MD driver - - -Overview -======== - -Linux-NTFS comes with a number of user-space programs known as ntfsprogs. -These include mkntfs, a full-featured ntfs filesystem format utility, -ntfsundelete used for recovering files that were unintentionally deleted -from an NTFS volume and ntfsresize which is used to resize an NTFS partition. -See the web site for more information. - -To mount an NTFS 1.2/3.x (Windows NT4/2000/XP/2003) volume, use the file -system type 'ntfs'. The driver currently supports read-only mode (with no -fault-tolerance, encryption or journalling) and very limited, but safe, write -support. - -For fault tolerance and raid support (i.e. volume and stripe sets), you can -use the kernel's Software RAID / MD driver. See section "Using Software RAID -with NTFS" for details. - - -Web site -======== - -There is plenty of additional information on the linux-ntfs web site -at http://www.linux-ntfs.org/ - -The web site has a lot of additional information, such as a comprehensive -FAQ, documentation on the NTFS on-disk format, information on the Linux-NTFS -userspace utilities, etc. - - -Features -======== - -- This is a complete rewrite of the NTFS driver that used to be in the 2.4 and - earlier kernels. This new driver implements NTFS read support and is - functionally equivalent to the old ntfs driver and it also implements limited - write support. The biggest limitation at present is that files/directories - cannot be created or deleted. See below for the list of write features that - are so far supported. Another limitation is that writing to compressed files - is not implemented at all. Also, neither read nor write access to encrypted - files is so far implemented. -- The new driver has full support for sparse files on NTFS 3.x volumes which - the old driver isn't happy with. -- The new driver supports execution of binaries due to mmap() now being - supported. -- The new driver supports loopback mounting of files on NTFS which is used by - some Linux distributions to enable the user to run Linux from an NTFS - partition by creating a large file while in Windows and then loopback - mounting the file while in Linux and creating a Linux filesystem on it that - is used to install Linux on it. -- A comparison of the two drivers using:: - - time find . -type f -exec md5sum "{}" \; - - run three times in sequence with each driver (after a reboot) on a 1.4GiB - NTFS partition, showed the new driver to be 20% faster in total time elapsed - (from 9:43 minutes on average down to 7:53). The time spent in user space - was unchanged but the time spent in the kernel was decreased by a factor of - 2.5 (from 85 CPU seconds down to 33). -- The driver does not support short file names in general. For backwards - compatibility, we implement access to files using their short file names if - they exist. The driver will not create short file names however, and a - rename will discard any existing short file name. -- The new driver supports exporting of mounted NTFS volumes via NFS. -- The new driver supports async io (aio). -- The new driver supports fsync(2), fdatasync(2), and msync(2). -- The new driver supports readv(2) and writev(2). -- The new driver supports access time updates (including mtime and ctime). -- The new driver supports truncate(2) and open(2) with O_TRUNC. But at present - only very limited support for highly fragmented files, i.e. ones which have - their data attribute split across multiple extents, is included. Another - limitation is that at present truncate(2) will never create sparse files, - since to mark a file sparse we need to modify the directory entry for the - file and we do not implement directory modifications yet. -- The new driver supports write(2) which can both overwrite existing data and - extend the file size so that you can write beyond the existing data. Also, - writing into sparse regions is supported and the holes are filled in with - clusters. But at present only limited support for highly fragmented files, - i.e. ones which have their data attribute split across multiple extents, is - included. Another limitation is that write(2) will never create sparse - files, since to mark a file sparse we need to modify the directory entry for - the file and we do not implement directory modifications yet. - -Supported mount options -======================= - -In addition to the generic mount options described by the manual page for the -mount command (man 8 mount, also see man 5 fstab), the NTFS driver supports the -following mount options: - -======================= ======================================================= -iocharset=name Deprecated option. Still supported but please use - nls=name in the future. See description for nls=name. - -nls=name Character set to use when returning file names. - Unlike VFAT, NTFS suppresses names that contain - unconvertible characters. Note that most character - sets contain insufficient characters to represent all - possible Unicode characters that can exist on NTFS. - To be sure you are not missing any files, you are - advised to use nls=utf8 which is capable of - representing all Unicode characters. - -utf8=<bool> Option no longer supported. Currently mapped to - nls=utf8 but please use nls=utf8 in the future and - make sure utf8 is compiled either as module or into - the kernel. See description for nls=name. - -uid= -gid= -umask= Provide default owner, group, and access mode mask. - These options work as documented in mount(8). By - default, the files/directories are owned by root and - he/she has read and write permissions, as well as - browse permission for directories. No one else has any - access permissions. I.e. the mode on all files is by - default rw------- and for directories rwx------, a - consequence of the default fmask=0177 and dmask=0077. - Using a umask of zero will grant all permissions to - everyone, i.e. all files and directories will have mode - rwxrwxrwx. - -fmask= -dmask= Instead of specifying umask which applies both to - files and directories, fmask applies only to files and - dmask only to directories. - -sloppy=<BOOL> If sloppy is specified, ignore unknown mount options. - Otherwise the default behaviour is to abort mount if - any unknown options are found. - -show_sys_files=<BOOL> If show_sys_files is specified, show the system files - in directory listings. Otherwise the default behaviour - is to hide the system files. - Note that even when show_sys_files is specified, "$MFT" - will not be visible due to bugs/mis-features in glibc. - Further, note that irrespective of show_sys_files, all - files are accessible by name, i.e. you can always do - "ls -l \$UpCase" for example to specifically show the - system file containing the Unicode upcase table. - -case_sensitive=<BOOL> If case_sensitive is specified, treat all file names as - case sensitive and create file names in the POSIX - namespace. Otherwise the default behaviour is to treat - file names as case insensitive and to create file names - in the WIN32/LONG name space. Note, the Linux NTFS - driver will never create short file names and will - remove them on rename/delete of the corresponding long - file name. - Note that files remain accessible via their short file - name, if it exists. If case_sensitive, you will need - to provide the correct case of the short file name. - -disable_sparse=<BOOL> If disable_sparse is specified, creation of sparse - regions, i.e. holes, inside files is disabled for the - volume (for the duration of this mount only). By - default, creation of sparse regions is enabled, which - is consistent with the behaviour of traditional Unix - filesystems. - -errors=opt What to do when critical filesystem errors are found. - Following values can be used for "opt": - - ======== ========================================= - continue DEFAULT, try to clean-up as much as - possible, e.g. marking a corrupt inode as - bad so it is no longer accessed, and then - continue. - recover At present only supported is recovery of - the boot sector from the backup copy. - If read-only mount, the recovery is done - in memory only and not written to disk. - ======== ========================================= - - Note that the options are additive, i.e. specifying:: - - errors=continue,errors=recover - - means the driver will attempt to recover and if that - fails it will clean-up as much as possible and - continue. - -mft_zone_multiplier= Set the MFT zone multiplier for the volume (this - setting is not persistent across mounts and can be - changed from mount to mount but cannot be changed on - remount). Values of 1 to 4 are allowed, 1 being the - default. The MFT zone multiplier determines how much - space is reserved for the MFT on the volume. If all - other space is used up, then the MFT zone will be - shrunk dynamically, so this has no impact on the - amount of free space. However, it can have an impact - on performance by affecting fragmentation of the MFT. - In general use the default. If you have a lot of small - files then use a higher value. The values have the - following meaning: - - ===== ================================= - Value MFT zone size (% of volume size) - ===== ================================= - 1 12.5% - 2 25% - 3 37.5% - 4 50% - ===== ================================= - - Note this option is irrelevant for read-only mounts. -======================= ======================================================= - - -Known bugs and (mis-)features -============================= - -- The link count on each directory inode entry is set to 1, due to Linux not - supporting directory hard links. This may well confuse some user space - applications, since the directory names will have the same inode numbers. - This also speeds up ntfs_read_inode() immensely. And we haven't found any - problems with this approach so far. If you find a problem with this, please - let us know. - - -Please send bug reports/comments/feedback/abuse to the Linux-NTFS development -list at sourceforge: linux-ntfs-dev@lists.sourceforge.net - - -Using NTFS volume and stripe sets -================================= - -For support of volume and stripe sets, you can either use the kernel's -Device-Mapper driver or the kernel's Software RAID / MD driver. The former is -the recommended one to use for linear raid. But the latter is required for -raid level 5. For striping and mirroring, either driver should work fine. - - -The Device-Mapper driver ------------------------- - -You will need to create a table of the components of the volume/stripe set and -how they fit together and load this into the kernel using the dmsetup utility -(see man 8 dmsetup). - -Linear volume sets, i.e. linear raid, has been tested and works fine. Even -though untested, there is no reason why stripe sets, i.e. raid level 0, and -mirrors, i.e. raid level 1 should not work, too. Stripes with parity, i.e. -raid level 5, unfortunately cannot work yet because the current version of the -Device-Mapper driver does not support raid level 5. You may be able to use the -Software RAID / MD driver for raid level 5, see the next section for details. - -To create the table describing your volume you will need to know each of its -components and their sizes in sectors, i.e. multiples of 512-byte blocks. - -For NT4 fault tolerant volumes you can obtain the sizes using fdisk. So for -example if one of your partitions is /dev/hda2 you would do:: - - $ fdisk -ul /dev/hda - - Disk /dev/hda: 81.9 GB, 81964302336 bytes - 255 heads, 63 sectors/track, 9964 cylinders, total 160086528 sectors - Units = sectors of 1 * 512 = 512 bytes - - Device Boot Start End Blocks Id System - /dev/hda1 * 63 4209029 2104483+ 83 Linux - /dev/hda2 4209030 37768814 16779892+ 86 NTFS - /dev/hda3 37768815 46170809 4200997+ 83 Linux - -And you would know that /dev/hda2 has a size of 37768814 - 4209030 + 1 = -33559785 sectors. - -For Win2k and later dynamic disks, you can for example use the ldminfo utility -which is part of the Linux LDM tools (the latest version at the time of -writing is linux-ldm-0.0.8.tar.bz2). You can download it from: - - http://www.linux-ntfs.org/ - -Simply extract the downloaded archive (tar xvjf linux-ldm-0.0.8.tar.bz2), go -into it (cd linux-ldm-0.0.8) and change to the test directory (cd test). You -will find the precompiled (i386) ldminfo utility there. NOTE: You will not be -able to compile this yourself easily so use the binary version! - -Then you would use ldminfo in dump mode to obtain the necessary information:: - - $ ./ldminfo --dump /dev/hda - -This would dump the LDM database found on /dev/hda which describes all of your -dynamic disks and all the volumes on them. At the bottom you will see the -VOLUME DEFINITIONS section which is all you really need. You may need to look -further above to determine which of the disks in the volume definitions is -which device in Linux. Hint: Run ldminfo on each of your dynamic disks and -look at the Disk Id close to the top of the output for each (the PRIVATE HEADER -section). You can then find these Disk Ids in the VBLK DATABASE section in the -<Disk> components where you will get the LDM Name for the disk that is found in -the VOLUME DEFINITIONS section. - -Note you will also need to enable the LDM driver in the Linux kernel. If your -distribution did not enable it, you will need to recompile the kernel with it -enabled. This will create the LDM partitions on each device at boot time. You -would then use those devices (for /dev/hda they would be /dev/hda1, 2, 3, etc) -in the Device-Mapper table. - -You can also bypass using the LDM driver by using the main device (e.g. -/dev/hda) and then using the offsets of the LDM partitions into this device as -the "Start sector of device" when creating the table. Once again ldminfo would -give you the correct information to do this. - -Assuming you know all your devices and their sizes things are easy. - -For a linear raid the table would look like this (note all values are in -512-byte sectors):: - - # Offset into Size of this Raid type Device Start sector - # volume device of device - 0 1028161 linear /dev/hda1 0 - 1028161 3903762 linear /dev/hdb2 0 - 4931923 2103211 linear /dev/hdc1 0 - -For a striped volume, i.e. raid level 0, you will need to know the chunk size -you used when creating the volume. Windows uses 64kiB as the default, so it -will probably be this unless you changes the defaults when creating the array. - -For a raid level 0 the table would look like this (note all values are in -512-byte sectors):: - - # Offset Size Raid Number Chunk 1st Start 2nd Start - # into of the type of size Device in Device in - # volume volume stripes device device - 0 2056320 striped 2 128 /dev/hda1 0 /dev/hdb1 0 - -If there are more than two devices, just add each of them to the end of the -line. - -Finally, for a mirrored volume, i.e. raid level 1, the table would look like -this (note all values are in 512-byte sectors):: - - # Ofs Size Raid Log Number Region Should Number Source Start Target Start - # in of the type type of log size sync? of Device in Device in - # vol volume params mirrors Device Device - 0 2056320 mirror core 2 16 nosync 2 /dev/hda1 0 /dev/hdb1 0 - -If you are mirroring to multiple devices you can specify further targets at the -end of the line. - -Note the "Should sync?" parameter "nosync" means that the two mirrors are -already in sync which will be the case on a clean shutdown of Windows. If the -mirrors are not clean, you can specify the "sync" option instead of "nosync" -and the Device-Mapper driver will then copy the entirety of the "Source Device" -to the "Target Device" or if you specified multiple target devices to all of -them. - -Once you have your table, save it in a file somewhere (e.g. /etc/ntfsvolume1), -and hand it over to dmsetup to work with, like so:: - - $ dmsetup create myvolume1 /etc/ntfsvolume1 - -You can obviously replace "myvolume1" with whatever name you like. - -If it all worked, you will now have the device /dev/device-mapper/myvolume1 -which you can then just use as an argument to the mount command as usual to -mount the ntfs volume. For example:: - - $ mount -t ntfs -o ro /dev/device-mapper/myvolume1 /mnt/myvol1 - -(You need to create the directory /mnt/myvol1 first and of course you can use -anything you like instead of /mnt/myvol1 as long as it is an existing -directory.) - -It is advisable to do the mount read-only to see if the volume has been setup -correctly to avoid the possibility of causing damage to the data on the ntfs -volume. - - -The Software RAID / MD driver ------------------------------ - -An alternative to using the Device-Mapper driver is to use the kernel's -Software RAID / MD driver. For which you need to set up your /etc/raidtab -appropriately (see man 5 raidtab). - -Linear volume sets, i.e. linear raid, as well as stripe sets, i.e. raid level -0, have been tested and work fine (though see section "Limitations when using -the MD driver with NTFS volumes" especially if you want to use linear raid). -Even though untested, there is no reason why mirrors, i.e. raid level 1, and -stripes with parity, i.e. raid level 5, should not work, too. - -You have to use the "persistent-superblock 0" option for each raid-disk in the -NTFS volume/stripe you are configuring in /etc/raidtab as the persistent -superblock used by the MD driver would damage the NTFS volume. - -Windows by default uses a stripe chunk size of 64k, so you probably want the -"chunk-size 64k" option for each raid-disk, too. - -For example, if you have a stripe set consisting of two partitions /dev/hda5 -and /dev/hdb1 your /etc/raidtab would look like this:: - - raiddev /dev/md0 - raid-level 0 - nr-raid-disks 2 - nr-spare-disks 0 - persistent-superblock 0 - chunk-size 64k - device /dev/hda5 - raid-disk 0 - device /dev/hdb1 - raid-disk 1 - -For linear raid, just change the raid-level above to "raid-level linear", for -mirrors, change it to "raid-level 1", and for stripe sets with parity, change -it to "raid-level 5". - -Note for stripe sets with parity you will also need to tell the MD driver -which parity algorithm to use by specifying the option "parity-algorithm -which", where you need to replace "which" with the name of the algorithm to -use (see man 5 raidtab for available algorithms) and you will have to try the -different available algorithms until you find one that works. Make sure you -are working read-only when playing with this as you may damage your data -otherwise. If you find which algorithm works please let us know (email the -linux-ntfs developers list linux-ntfs-dev@lists.sourceforge.net or drop in on -IRC in channel #ntfs on the irc.freenode.net network) so we can update this -documentation. - -Once the raidtab is setup, run for example raid0run -a to start all devices or -raid0run /dev/md0 to start a particular md device, in this case /dev/md0. - -Then just use the mount command as usual to mount the ntfs volume using for -example:: - - mount -t ntfs -o ro /dev/md0 /mnt/myntfsvolume - -It is advisable to do the mount read-only to see if the md volume has been -setup correctly to avoid the possibility of causing damage to the data on the -ntfs volume. - - -Limitations when using the Software RAID / MD driver ------------------------------------------------------ - -Using the md driver will not work properly if any of your NTFS partitions have -an odd number of sectors. This is especially important for linear raid as all -data after the first partition with an odd number of sectors will be offset by -one or more sectors so if you mount such a partition with write support you -will cause massive damage to the data on the volume which will only become -apparent when you try to use the volume again under Windows. - -So when using linear raid, make sure that all your partitions have an even -number of sectors BEFORE attempting to use it. You have been warned! - -Even better is to simply use the Device-Mapper for linear raid and then you do -not have this problem with odd numbers of sectors. diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst index 1c244866041a..165514401441 100644 --- a/Documentation/filesystems/overlayfs.rst +++ b/Documentation/filesystems/overlayfs.rst @@ -145,7 +145,9 @@ filesystem, an overlay filesystem needs to record in the upper filesystem that files have been removed. This is done using whiteouts and opaque directories (non-directories are always opaque). -A whiteout is created as a character device with 0/0 device number. +A whiteout is created as a character device with 0/0 device number or +as a zero-size regular file with the xattr "trusted.overlay.whiteout". + When a whiteout is found in the upper level of a merged directory, any matching name in the lower level is ignored, and the whiteout itself is also hidden. @@ -154,6 +156,13 @@ A directory is made opaque by setting the xattr "trusted.overlay.opaque" to "y". Where the upper filesystem contains an opaque directory, any directory in the lower filesystem with the same name is ignored. +An opaque directory should not conntain any whiteouts, because they do not +serve any purpose. A merge directory containing regular files with the xattr +"trusted.overlay.whiteout", should be additionally marked by setting the xattr +"trusted.overlay.opaque" to "x" on the merge directory itself. +This is needed to avoid the overhead of checking the "trusted.overlay.whiteout" +on all entries during readdir in the common case. + readdir ------- @@ -534,8 +543,9 @@ A lower dir with a regular whiteout will always be handled by the overlayfs mount, so to support storing an effective whiteout file in an overlayfs mount an alternative form of whiteout is supported. This form is a regular, zero-size file with the "overlay.whiteout" xattr set, inside a directory with the -"overlay.whiteouts" xattr set. Such whiteouts are never created by overlayfs, -but can be used by userspace tools (like containers) that generate lower layers. +"overlay.opaque" xattr set to "x" (see `whiteouts and opaque directories`_). +These alternative whiteouts are never created by overlayfs, but can be used by +userspace tools (like containers) that generate lower layers. These alternative whiteouts can be escaped using the standard xattr escape mechanism in order to properly nest to any depth. diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 104c6d047d9b..c6a6b9df2104 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -1899,8 +1899,8 @@ For more information on mount propagation see: These files provide a method to access a task's comm value. It also allows for a task to set its own or one of its thread siblings comm value. The comm value is limited in size compared to the cmdline value, so writing anything longer -then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated -comm value. +then the kernel's TASK_COMM_LEN (currently 16 chars, including the NUL +terminator) will result in a truncated comm value. 3.7 /proc/<pid>/task/<tid>/children - Information about task children diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index eebcc0f9e2bc..6e903a903f8f 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -1264,7 +1264,7 @@ defined: char *(*d_dname)(struct dentry *, char *, int); struct vfsmount *(*d_automount)(struct path *); int (*d_manage)(const struct path *, bool); - struct dentry *(*d_real)(struct dentry *, const struct inode *); + struct dentry *(*d_real)(struct dentry *, enum d_real_type type); }; ``d_revalidate`` @@ -1419,16 +1419,14 @@ defined: the dentry being transited from. ``d_real`` - overlay/union type filesystems implement this method to return - one of the underlying dentries hidden by the overlay. It is - used in two different modes: + overlay/union type filesystems implement this method to return one + of the underlying dentries of a regular file hidden by the overlay. - Called from file_dentry() it returns the real dentry matching - the inode argument. The real dentry may be from a lower layer - already copied up, but still referenced from the file. This - mode is selected with a non-NULL inode argument. + The 'type' argument takes the values D_REAL_DATA or D_REAL_METADATA + for returning the real underlying dentry that refers to the inode + hosting the file's data or metadata respectively. - With NULL inode the topmost real underlying dentry is returned. + For non-regular files, the 'dentry' argument is returned. Each dentry has a pointer to its parent dentry, as well as a hash list of child dentries. Child dentries are basically like files in a diff --git a/Documentation/filesystems/xfs/xfs-online-fsck-design.rst b/Documentation/filesystems/xfs/xfs-online-fsck-design.rst index 352516feef6f..6333697ba3e8 100644 --- a/Documentation/filesystems/xfs/xfs-online-fsck-design.rst +++ b/Documentation/filesystems/xfs/xfs-online-fsck-design.rst @@ -1915,19 +1915,13 @@ four of those five higher level data structures. The fifth use case is discussed in the :ref:`realtime summary <rtsummary>` case study. -The most general storage interface supported by the xfile enables the reading -and writing of arbitrary quantities of data at arbitrary offsets in the xfile. -This capability is provided by ``xfile_pread`` and ``xfile_pwrite`` functions, -which behave similarly to their userspace counterparts. XFS is very record-based, which suggests that the ability to load and store complete records is important. -To support these cases, a pair of ``xfile_obj_load`` and ``xfile_obj_store`` -functions are provided to read and persist objects into an xfile. -They are internally the same as pread and pwrite, except that they treat any -error as an out of memory error. -For online repair, squashing error conditions in this manner is an acceptable -behavior because the only reaction is to abort the operation back to userspace. -All five xfile usecases can be serviced by these four functions. +To support these cases, a pair of ``xfile_load`` and ``xfile_store`` +functions are provided to read and persist objects into an xfile that treat any +error as an out of memory error. For online repair, squashing error conditions +in this manner is an acceptable behavior because the only reaction is to abort +the operation back to userspace. However, no discussion of file access idioms is complete without answering the question, "But what about mmap?" @@ -1939,15 +1933,14 @@ tmpfs can only push a pagecache folio to the swap cache if the folio is neither pinned nor locked, which means the xfile must not pin too many folios. Short term direct access to xfile contents is done by locking the pagecache -folio and mapping it into kernel address space. -Programmatic access (e.g. pread and pwrite) uses this mechanism. -Folio locks are not supposed to be held for long periods of time, so long -term direct access to xfile contents is done by bumping the folio refcount, +folio and mapping it into kernel address space. Object load and store uses this +mechanism. Folio locks are not supposed to be held for long periods of time, so +long term direct access to xfile contents is done by bumping the folio refcount, mapping it into kernel address space, and dropping the folio lock. These long term users *must* be responsive to memory reclaim by hooking into the shrinker infrastructure to know when to release folios. -The ``xfile_get_page`` and ``xfile_put_page`` functions are provided to +The ``xfile_get_folio`` and ``xfile_put_folio`` functions are provided to retrieve the (locked) folio that backs part of an xfile and to release it. The only code to use these folio lease functions are the xfarray :ref:`sorting<xfarray_sort>` algorithms and the :ref:`in-memory @@ -2277,13 +2270,12 @@ follows: pointing to the xfile. 3. Pass the buffer cache target, buffer ops, and other information to - ``xfbtree_create`` to write an initial tree header and root block to the - xfile. + ``xfbtree_init`` to initialize the passed in ``struct xfbtree`` and write an + initial root block to the xfile. Each btree type should define a wrapper that passes necessary arguments to the creation function. For example, rmap btrees define ``xfs_rmapbt_mem_create`` to take care of all the necessary details for callers. - A ``struct xfbtree`` object will be returned. 4. Pass the xfbtree object to the btree cursor creation function for the btree type. |