From c9c4ff12df110feb1b91951010f673f4b16e49e8 Mon Sep 17 00:00:00 2001 From: David Howells Date: Mon, 27 Nov 2023 13:58:07 +0000 Subject: netfs: Move pinning-for-writeback from fscache to netfs Move the resource pinning-for-writeback from fscache code to netfslib code. This is used to keep a cache backing object pinned whilst we have dirty pages on the netfs inode in the pagecache such that VM writeback will be able to reach it. Whilst we're at it, switch the parameters of netfs_unpin_writeback() to match ->write_inode() so that it can be used for that directly. Note that this mechanism could be more generically useful than that for network filesystems. Quite often they have to keep around other resources (e.g. authentication tokens or network connections) until the writeback is complete. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/misc.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 86 insertions(+) create mode 100644 fs/netfs/misc.c (limited to 'fs/netfs/misc.c') diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c new file mode 100644 index 000000000000..68baf55c47a4 --- /dev/null +++ b/fs/netfs/misc.c @@ -0,0 +1,86 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Miscellaneous routines. + * + * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include +#include "internal.h" + +/** + * netfs_dirty_folio - Mark folio dirty and pin a cache object for writeback + * @mapping: The mapping the folio belongs to. + * @folio: The folio being dirtied. + * + * Set the dirty flag on a folio and pin an in-use cache object in memory so + * that writeback can later write to it. This is intended to be called from + * the filesystem's ->dirty_folio() method. + * + * Return: true if the dirty flag was set on the folio, false otherwise. + */ +bool netfs_dirty_folio(struct address_space *mapping, struct folio *folio) +{ + struct inode *inode = mapping->host; + struct netfs_inode *ictx = netfs_inode(inode); + struct fscache_cookie *cookie = netfs_i_cookie(ictx); + bool need_use = false; + + _enter(""); + + if (!filemap_dirty_folio(mapping, folio)) + return false; + if (!fscache_cookie_valid(cookie)) + return true; + + if (!(inode->i_state & I_PINNING_NETFS_WB)) { + spin_lock(&inode->i_lock); + if (!(inode->i_state & I_PINNING_NETFS_WB)) { + inode->i_state |= I_PINNING_NETFS_WB; + need_use = true; + } + spin_unlock(&inode->i_lock); + + if (need_use) + fscache_use_cookie(cookie, true); + } + return true; +} +EXPORT_SYMBOL(netfs_dirty_folio); + +/** + * netfs_unpin_writeback - Unpin writeback resources + * @inode: The inode on which the cookie resides + * @wbc: The writeback control + * + * Unpin the writeback resources pinned by netfs_dirty_folio(). This is + * intended to be called as/by the netfs's ->write_inode() method. + */ +int netfs_unpin_writeback(struct inode *inode, struct writeback_control *wbc) +{ + struct fscache_cookie *cookie = netfs_i_cookie(netfs_inode(inode)); + + if (wbc->unpinned_netfs_wb) + fscache_unuse_cookie(cookie, NULL, NULL); + return 0; +} +EXPORT_SYMBOL(netfs_unpin_writeback); + +/** + * netfs_clear_inode_writeback - Clear writeback resources pinned by an inode + * @inode: The inode to clean up + * @aux: Auxiliary data to apply to the inode + * + * Clear any writeback resources held by an inode when the inode is evicted. + * This must be called before clear_inode() is called. + */ +void netfs_clear_inode_writeback(struct inode *inode, const void *aux) +{ + struct fscache_cookie *cookie = netfs_i_cookie(netfs_inode(inode)); + + if (inode->i_state & I_PINNING_NETFS_WB) { + loff_t i_size = i_size_read(inode); + fscache_unuse_cookie(cookie, aux, &i_size); + } +} +EXPORT_SYMBOL(netfs_clear_inode_writeback); -- cgit From c1ec4d7c2e13471558cfea302b7583856284f94c Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 20 Aug 2021 17:08:30 +0100 Subject: netfs: Provide invalidate_folio and release_folio calls Provide default invalidate_folio and release_folio calls. These will need to interact with invalidation correctly at some point. They will be needed if netfslib is to make use of folio->private for its own purposes. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/misc.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) (limited to 'fs/netfs/misc.c') diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c index 68baf55c47a4..45bb19ec9a63 100644 --- a/fs/netfs/misc.c +++ b/fs/netfs/misc.c @@ -84,3 +84,45 @@ void netfs_clear_inode_writeback(struct inode *inode, const void *aux) } } EXPORT_SYMBOL(netfs_clear_inode_writeback); + +/** + * netfs_invalidate_folio - Invalidate or partially invalidate a folio + * @folio: Folio proposed for release + * @offset: Offset of the invalidated region + * @length: Length of the invalidated region + * + * Invalidate part or all of a folio for a network filesystem. The folio will + * be removed afterwards if the invalidated region covers the entire folio. + */ +void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length) +{ + _enter("{%lx},%zx,%zx", folio_index(folio), offset, length); + + folio_wait_fscache(folio); +} +EXPORT_SYMBOL(netfs_invalidate_folio); + +/** + * netfs_release_folio - Try to release a folio + * @folio: Folio proposed for release + * @gfp: Flags qualifying the release + * + * Request release of a folio and clean up its private state if it's not busy. + * Returns true if the folio can now be released, false if not + */ +bool netfs_release_folio(struct folio *folio, gfp_t gfp) +{ + struct netfs_inode *ctx = netfs_inode(folio_inode(folio)); + + if (folio_test_private(folio)) + return false; + if (folio_test_fscache(folio)) { + if (current_is_kswapd() || !(gfp & __GFP_FS)) + return false; + folio_wait_fscache(folio); + } + + fscache_note_page_release(netfs_i_cookie(ctx)); + return true; +} +EXPORT_SYMBOL(netfs_release_folio); -- cgit From 7d828a06634799aba0fa392913c7fe2953eb64a6 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 22 Sep 2023 13:25:22 +0100 Subject: netfs: Provide tools to create a buffer in an xarray Provide tools to create a buffer in an xarray, with a function to add new folios with a mark. This will be used to create bounce buffer and can be used more easily to create a list of folios the span of which would require more than a page's worth of bio_vec structs. Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/misc.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) (limited to 'fs/netfs/misc.c') diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c index 45bb19ec9a63..5d545073fe03 100644 --- a/fs/netfs/misc.c +++ b/fs/netfs/misc.c @@ -8,6 +8,87 @@ #include #include "internal.h" +/* + * Attach a folio to the buffer and maybe set marks on it to say that we need + * to put the folio later and twiddle the pagecache flags. + */ +int netfs_xa_store_and_mark(struct xarray *xa, unsigned long index, + struct folio *folio, unsigned int flags, + gfp_t gfp_mask) +{ + XA_STATE_ORDER(xas, xa, index, folio_order(folio)); + +retry: + xas_lock(&xas); + for (;;) { + xas_store(&xas, folio); + if (!xas_error(&xas)) + break; + xas_unlock(&xas); + if (!xas_nomem(&xas, gfp_mask)) + return xas_error(&xas); + goto retry; + } + + if (flags & NETFS_FLAG_PUT_MARK) + xas_set_mark(&xas, NETFS_BUF_PUT_MARK); + if (flags & NETFS_FLAG_PAGECACHE_MARK) + xas_set_mark(&xas, NETFS_BUF_PAGECACHE_MARK); + xas_unlock(&xas); + return xas_error(&xas); +} + +/* + * Create the specified range of folios in the buffer attached to the read + * request. The folios are marked with NETFS_BUF_PUT_MARK so that we know that + * these need freeing later. + */ +int netfs_add_folios_to_buffer(struct xarray *buffer, + struct address_space *mapping, + pgoff_t index, pgoff_t to, gfp_t gfp_mask) +{ + struct folio *folio; + int ret; + + if (to + 1 == index) /* Page range is inclusive */ + return 0; + + do { + /* TODO: Figure out what order folio can be allocated here */ + folio = filemap_alloc_folio(readahead_gfp_mask(mapping), 0); + if (!folio) + return -ENOMEM; + folio->index = index; + ret = netfs_xa_store_and_mark(buffer, index, folio, + NETFS_FLAG_PUT_MARK, gfp_mask); + if (ret < 0) { + folio_put(folio); + return ret; + } + + index += folio_nr_pages(folio); + } while (index <= to && index != 0); + + return 0; +} + +/* + * Clear an xarray buffer, putting a ref on the folios that have + * NETFS_BUF_PUT_MARK set. + */ +void netfs_clear_buffer(struct xarray *buffer) +{ + struct folio *folio; + XA_STATE(xas, buffer, 0); + + rcu_read_lock(); + xas_for_each_marked(&xas, folio, ULONG_MAX, NETFS_BUF_PUT_MARK) { + folio_put(folio); + } + rcu_read_unlock(); + xa_destroy(buffer); +} + /** * netfs_dirty_folio - Mark folio dirty and pin a cache object for writeback * @mapping: The mapping the folio belongs to. -- cgit From 9ebff83e648148b9ece97d4e4890dd84ca54d6ce Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 29 Sep 2023 17:28:25 +0100 Subject: netfs: Prep to use folio->private for write grouping and streaming write Prepare to use folio->private to hold information write grouping and streaming write. These are implemented in the same commit as they both make use of folio->private and will be both checked at the same time in several places. "Write grouping" involves ordering the writeback of groups of writes, such as is needed for ceph snaps. A group is represented by a filesystem-supplied object which must contain a netfs_group struct. This contains just a refcount and a pointer to a destructor. "Streaming write" is the storage of data in folios that are marked dirty, but not uptodate, to avoid unnecessary reads of data. This is represented by a netfs_folio struct. This contains the offset and length of the modified region plus the otherwise displaced write grouping pointer. The way folio->private is multiplexed is: (1) If private is NULL then neither is in operation on a dirty folio. (2) If private is set, with bit 0 clear, then this points to a group. (3) If private is set, with bit 0 set, then this points to a netfs_folio struct (with bit 0 AND'ed out). Signed-off-by: David Howells Reviewed-by: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/misc.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) (limited to 'fs/netfs/misc.c') diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c index 5d545073fe03..eeb44abe59c5 100644 --- a/fs/netfs/misc.c +++ b/fs/netfs/misc.c @@ -177,9 +177,55 @@ EXPORT_SYMBOL(netfs_clear_inode_writeback); */ void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length) { + struct netfs_folio *finfo = NULL; + size_t flen = folio_size(folio); + _enter("{%lx},%zx,%zx", folio_index(folio), offset, length); folio_wait_fscache(folio); + + if (!folio_test_private(folio)) + return; + + finfo = netfs_folio_info(folio); + + if (offset == 0 && length >= flen) + goto erase_completely; + + if (finfo) { + /* We have a partially uptodate page from a streaming write. */ + unsigned int fstart = finfo->dirty_offset; + unsigned int fend = fstart + finfo->dirty_len; + unsigned int end = offset + length; + + if (offset >= fend) + return; + if (end <= fstart) + return; + if (offset <= fstart && end >= fend) + goto erase_completely; + if (offset <= fstart && end > fstart) + goto reduce_len; + if (offset > fstart && end >= fend) + goto move_start; + /* A partial write was split. The caller has already zeroed + * it, so just absorb the hole. + */ + } + return; + +erase_completely: + netfs_put_group(netfs_folio_group(folio)); + folio_detach_private(folio); + folio_clear_uptodate(folio); + kfree(finfo); + return; +reduce_len: + finfo->dirty_len = offset + length - finfo->dirty_offset; + return; +move_start: + finfo->dirty_len -= offset - finfo->dirty_offset; + finfo->dirty_offset = offset; } EXPORT_SYMBOL(netfs_invalidate_folio); -- cgit From 100ccd18bb41ea7abb4fbb419202c06079559501 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 24 Nov 2023 13:39:02 +0000 Subject: netfs: Optimise away reads above the point at which there can be no data Track the file position above which the server is not expected to have any data (the "zero point") and preemptively assume that we can satisfy requests by filling them with zeroes locally rather than attempting to download them if they're over that line - even if we've written data back to the server. Assume that any data that was written back above that position is held in the local cache. Note that we have to split requests that straddle the line. Make use of this to optimise away some reads from the server. We need to set the zero point in the following circumstances: (1) When we see an extant remote inode and have no cache for it, we set the zero_point to i_size. (2) On local inode creation, we set zero_point to 0. (3) On local truncation down, we reduce zero_point to the new i_size if the new i_size is lower. (4) On local truncation up, we don't change zero_point. (5) On local modification, we don't change zero_point. (6) On remote invalidation, we set zero_point to the new i_size. (7) If stored data is discarded from the pagecache or culled from fscache, we must set zero_point above that if the data also got written to the server. (8) If dirty data is written back to the server, but not fscache, we must set zero_point above that. (9) If a direct I/O write is made, set zero_point above that. Assuming the above, any read from the server at or above the zero_point position will return all zeroes. The zero_point value can be stored in the cache, provided the above rules are applied to it by any code that culls part of the local cache. Signed-off-by: David Howells cc: Jeff Layton cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- fs/netfs/misc.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'fs/netfs/misc.c') diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c index eeb44abe59c5..0e3af37fc924 100644 --- a/fs/netfs/misc.c +++ b/fs/netfs/misc.c @@ -240,6 +240,11 @@ EXPORT_SYMBOL(netfs_invalidate_folio); bool netfs_release_folio(struct folio *folio, gfp_t gfp) { struct netfs_inode *ctx = netfs_inode(folio_inode(folio)); + unsigned long long end; + + end = folio_pos(folio) + folio_size(folio); + if (end > ctx->zero_point) + ctx->zero_point = end; if (folio_test_private(folio)) return false; -- cgit From 202bc57b675601bc07b5942369ecc16af64d1b95 Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 9 Jan 2024 17:17:36 +0000 Subject: netfs: Don't use certain unnecessary folio_*() functions Filesystems should use folio->index and folio->mapping, instead of folio_index(folio), folio_mapping() and folio_file_mapping() since they know that it's in the pagecache. Change this automagically with: perl -p -i -e 's/folio_mapping[(]([^)]*)[)]/\1->mapping/g' fs/netfs/*.c perl -p -i -e 's/folio_file_mapping[(]([^)]*)[)]/\1->mapping/g' fs/netfs/*.c perl -p -i -e 's/folio_index[(]([^)]*)[)]/\1->index/g' fs/netfs/*.c Reported-by: Matthew Wilcox Signed-off-by: David Howells cc: Jeff Layton cc: linux-afs@lists.infradead.org cc: linux-cachefs@redhat.com cc: linux-cifs@vger.kernel.org cc: linux-erofs@lists.ozlabs.org cc: linux-fsdevel@vger.kernel.org --- fs/netfs/misc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/netfs/misc.c') diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c index 0e3af37fc924..90051ced8e2a 100644 --- a/fs/netfs/misc.c +++ b/fs/netfs/misc.c @@ -180,7 +180,7 @@ void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length) struct netfs_folio *finfo = NULL; size_t flen = folio_size(folio); - _enter("{%lx},%zx,%zx", folio_index(folio), offset, length); + _enter("{%lx},%zx,%zx", folio->index, offset, length); folio_wait_fscache(folio); -- cgit