linux.git/fs/fuse/file.c, branch v6.16

fuse: fix fuse_fill_write_pages() upper bound calculation

2025-06-24T09:07:19+00:00

This fixes a bug in commit 63c69ad3d18a ("fuse: refactor
fuse_fill_write_pages()") where max_pages << PAGE_SHIFT is mistakenly
used as the calculation for the max_pages upper limit but there's the
possibility that copy_folio_from_iter_atomic() may copy over bytes
from the iov_iter that are less than the full length of the folio,
which would lead to exceeding max_pages.

This commit fixes it by adding a 'ap->num_folios < max_folios' check.

Signed-off-by: Joanne Koong 
Link: https://lore.kernel.org/20250614000114.910380-1-joannelkoong@gmail.com
Fixes: 63c69ad3d18a ("fuse: refactor fuse_fill_write_pages()")
Tested-by: Brian Foster 
Reported-by: Brian Foster 
Closes: https://lore.kernel.org/linux-fsdevel/aEq4haEQScwHIWK6@bfoster/
Signed-off-by: Christian Brauner

Merge tag 'fuse-update-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2025-06-02T22:31:05+00:00

Pull fuse updates from Miklos Szeredi:

 - Remove tmp page copying in writeback path (Joanne).

   This removes ~300 lines and with that a lot of complexity related to
   avoiding reclaim related deadlock. The old mechanism is replaced with
   a mapping flag that tells the MM not to block reclaim waiting for
   writeback to complete. The MM parts have been reviewed/acked by
   respective maintainers.

 - Convert more code to handle large folios (Joanne). This still just
   adds the code to deal with large folios and does not enable them yet.

 - Allow invalidating all cached lookups atomically (Luis Henriques).
   This feature is useful for CernVMFS, which currently does this
   iteratively.

 - Align write prefaulting in fuse with generic one (Dave Hansen)

 - Fix race causing invalid data to be cached when setting attributes on
   different nodes of a distributed fs (Guang Yuan Wu)

 - Update documentation for passthrough (Chen Linxuan)

 - Add fdinfo about the device number associated with an opened
   /dev/fuse instance (Chen Linxuan)

 - Increase readdir buffer size (Miklos). This depends on a patch to VFS
   readdir code that was already merged through Christians tree.

 - Optimize io-uring request expiration (Joanne)

 - Misc cleanups

* tag 'fuse-update-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (25 commits)
  fuse: increase readdir buffer size
  readdir: supply dir_context.count as readdir buffer size hint
  fuse: don't allow signals to interrupt getdents copying
  fuse: support large folios for writeback
  fuse: support large folios for readahead
  fuse: support large folios for queued writes
  fuse: support large folios for stores
  fuse: support large folios for symlinks
  fuse: support large folios for folio reads
  fuse: support large folios for writethrough writes
  fuse: refactor fuse_fill_write_pages()
  fuse: support large folios for retrieves
  fuse: support copying large folios
  fs: fuse: add dev id to /dev/fuse fdinfo
  docs: filesystems: add fuse-passthrough.rst
  MAINTAINERS: update filter of FUSE documentation
  fuse: fix race between concurrent setattrs from multiple nodes
  fuse: remove tmp folio for writebacks and internal rb tree
  mm: skip folio reclaim in legacy memcg contexts for deadlockable mappings
  fuse: optimize over-io-uring request expiration check
  ...

fuse: support large folios for writeback

2025-05-29T10:31:23+00:00

Add support for folios larger than one page size for writeback.

Signed-off-by: Joanne Koong 
Reviewed-by: Josef Bacik 
Reviewed-by: Jeff Layton 
Signed-off-by: Miklos Szeredi

fuse: support large folios for readahead

2025-05-29T10:31:23+00:00

Add support for folios larger than one page size for readahead.

Signed-off-by: Joanne Koong 
Reviewed-by: Jeff Layton 
Signed-off-by: Miklos Szeredi

fuse: support large folios for queued writes

2025-05-29T10:31:23+00:00

Add support for folios larger than one page size for queued writes.

Signed-off-by: Joanne Koong 
Reviewed-by: Josef Bacik 
Reviewed-by: Jeff Layton 
Reviewed-by: Bernd Schubert 
Signed-off-by: Miklos Szeredi

fuse: support large folios for folio reads

2025-05-29T10:31:23+00:00

Add support for folios larger than one page size for folio reads into
the page cache.

Signed-off-by: Joanne Koong 
Reviewed-by: Josef Bacik 
Reviewed-by: Jeff Layton 
Reviewed-by: Bernd Schubert 
Signed-off-by: Miklos Szeredi

fuse: support large folios for writethrough writes

2025-05-29T10:31:23+00:00

Add support for folios larger than one page size for writethrough
writes.

Signed-off-by: Joanne Koong 
Reviewed-by: Jeff Layton 
Signed-off-by: Miklos Szeredi

fuse: refactor fuse_fill_write_pages()

2025-05-29T10:31:23+00:00

Refactor the logic in fuse_fill_write_pages() for copying out write
data. This will make the future change for supporting large folios for
writes easier. No functional changes.

Signed-off-by: Joanne Koong 
Reviewed-by: Josef Bacik 
Reviewed-by: Jeff Layton 
Reviewed-by: Bernd Schubert 
Signed-off-by: Miklos Szeredi

fuse: drop usage of folio_index

2025-05-13T06:50:50+00:00

Patch series "mm, swap: clean up swap cache mapping helper", v3.

This series removes usage of folio_index usage in fs/, and remove swap
cache checking in folio_contains.

Currently, the swap cache is already no longer directly exposed to fs, and
swap cache will be more different from page cache.  Clean up the helpers
first to simplify the code and eliminate the helpers used for resolving
circular header dependency issue between filemap and swap headers, and
prepare for further changes.


This patch (of 6):

folio_index is only needed for mixed usage of page cache and swap cache,
for pure page cache usage, the caller can just use folio->index instead.

It can't be a swap cache folio here.  Swap mapping may only call into fs
through `swap_rw` but fuse does not use that method for SWAP.

Link: https://lkml.kernel.org/r/20250430181052.55698-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20250430181052.55698-2-ryncsn@gmail.com
Signed-off-by: Kairui Song 
Reviewed-by: Matthew Wilcox (Oracle) 
Reviewed-by: David Hildenbrand 
Cc: Miklos Szeredi 
Cc: Joanne Koong 
Cc: Josef Bacik 
Cc: Chris Li 
Cc: "Huang, Ying" 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: Nhat Pham 
Cc: Yosry Ahmed 
Cc: Christian Brauner 
Cc: Chao Yu 
Cc: Chris Mason 
Cc: David Sterba 
Cc: Jaegeuk Kim 
Cc: Qu Wenruo 
Signed-off-by: Andrew Morton

fuse: remove tmp folio for writebacks and internal rb tree

2025-04-15T12:23:28+00:00

In the current FUSE writeback design (see commit 3be5a52b30aa
("fuse: support writable mmap")), a temp page is allocated for every
dirty page to be written back, the contents of the dirty page are copied
over to the temp page, and the temp page gets handed to the server to
write back.

This is done so that writeback may be immediately cleared on the dirty
page, and this in turn is done in order to mitigate the following
deadlock scenario that may arise if reclaim waits on writeback on the
dirty page to complete:
* single-threaded FUSE server is in the middle of handling a request
  that needs a memory allocation
* memory allocation triggers direct reclaim
* direct reclaim waits on a folio under writeback
* the FUSE server can't write back the folio since it's stuck in
  direct reclaim

With a recent change that added AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM and
mitigates the situation described above, FUSE writeback does not need
to use temp pages if it sets AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM on its
inode mappings.

This commit sets AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM on the inode
mappings and removes the temporary pages + extra copying and the internal
rb tree.

fio benchmarks --
(using averages observed from 10 runs, throwing away outliers)

Setup:
sudo mount -t tmpfs -o size=30G tmpfs ~/tmp_mount
 ./libfuse/build/example/passthrough_ll -o writeback -o max_threads=4 -o source=~/tmp_mount ~/fuse_mount

fio --name=writeback --ioengine=sync --rw=write --bs={1k,4k,1M} --size=2G
--numjobs=2 --ramp_time=30 --group_reporting=1 --directory=/root/fuse_mount

        bs =  1k          4k            1M
Before  351 MiB/s     1818 MiB/s     1851 MiB/s
After   341 MiB/s     2246 MiB/s     2685 MiB/s
% diff        -3%          23%         45%

Signed-off-by: Joanne Koong 
Reviewed-by: Jingbo Xu 
Reviewed-by: Jeff Layton 
Signed-off-by: Miklos Szeredi