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netfs: Fix trimming of streaming-write folios in netfs_inval_folio()

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When netfslib writes to a folio that it doesn't have data for, but that
data exists on the server, it will make a 'streaming write' whereby it
stores data in a folio that is marked dirty, but not uptodate.  When it
does this, it attaches a record to folio->private to track the dirty
region.

When truncate() or fallocate() wants to invalidate part of such a folio, it
will call into ->invalidate_folio(), specifying the part of the folio that
is to be invalidated.  netfs_invalidate_folio(), on behalf of the
filesystem, must then determine how to trim the streaming write record.  In
a couple of cases, however, it does this incorrectly (the reduce-length and
move-start cases are switched over and don't, in any case, calculate the
value correctly).

Fix this by making the logic tree more obvious and fixing the cases.

Fixes: 9ebff83e64 ("netfs: Prep to use folio->private for write grouping and streaming write")
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20240823200819.532106-5-dhowells@redhat.com
cc: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Pankaj Raghav <p.raghav@samsung.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: netfs@lists.linux.dev
cc: linux-mm@kvack.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
David Howells 2024-08-23 21:08:12 +01:00 committed by Christian Brauner
parent 7dfc8f0c61
commit cce6bfa6ca
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 35 additions and 15 deletions
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50
fs/netfs/misc.c
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@ -97,10 +97,20 @@ EXPORT_SYMBOL(netfs_clear_inode_writeback);
void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
{
struct netfs_folio *finfo;
struct netfs_inode *ctx = netfs_inode(folio_inode(folio));
size_t flen = folio_size(folio);
_enter("{%lx},%zx,%zx", folio->index, offset, length);
if (offset == 0 && length == flen) {
unsigned long long i_size = i_size_read(&ctx->inode);
unsigned long long fpos = folio_pos(folio), end;
end = umin(fpos + flen, i_size);
if (fpos < i_size && end > ctx->zero_point)
ctx->zero_point = end;
}
folio_wait_private_2(folio); /* [DEPRECATED] */
if (!folio_test_private(folio))
@ -115,18 +125,34 @@ void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
/* 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;
unsigned int iend = offset + length;
if (offset >= fend)
return;
if (end <= fstart)
if (iend <= 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;
/* The invalidation region overlaps the data. If the region
* covers the start of the data, we either move along the start
* or just erase the data entirely.
*/
if (offset <= fstart) {
if (iend >= fend)
goto erase_completely;
/* Move the start of the data. */
finfo->dirty_len = fend - iend;
finfo->dirty_offset = offset;
return;
}
/* Reduce the length of the data if the invalidation region
* covers the tail part.
*/
if (iend >= fend) {
finfo->dirty_len = offset - fstart;
return;
}
/* A partial write was split. The caller has already zeroed
* it, so just absorb the hole.
*/
@ -139,12 +165,6 @@ erase_completely:
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);
@ -164,7 +184,7 @@ bool netfs_release_folio(struct folio *folio, gfp_t gfp)
if (folio_test_dirty(folio))
return false;
end = folio_pos(folio) + folio_size(folio);
end = umin(folio_pos(folio) + folio_size(folio), i_size_read(&ctx->inode));
if (end > ctx->zero_point)
ctx->zero_point = end;