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  1. 24 Apr, 2019 5 commits
    • Kirill Smelkov's avatar
      fuse: retrieve: cap requested size to negotiated max_write · 7640682e
      Kirill Smelkov authored 
      FUSE filesystem server and kernel client negotiate during initialization
phase, what should be the maximum write size the client will ever issue.
Correspondingly the filesystem server then queues sys_read calls to read
requests with buffer capacity large enough to carry request header + that
max_write bytes. A filesystem server is free to set its max_write in
anywhere in the range between [1*page, fc->max_pages*page]. In particular
go-fuse[2] sets max_write by default as 64K, wheres default fc->max_pages
corresponds to 128K. Libfuse also allows users to configure max_write, but
by default presets it to possible maximum.

If max_write is < fc->max_pages*page, and in NOTIFY_RETRIEVE handler we
allow to retrieve more than max_write bytes, corresponding prepared
NOTIFY_REPLY will be thrown away by fuse_dev_do_read, because the
filesystem server, in full correspondence with server/client contract, will
be only queuing sys_read with ~max_write buffer capacity, and
fuse_dev_do_read throws away requests that cannot fit into server request
buffer. In turn the filesystem server could get stuck waiting indefinitely
for NOTIFY_REPLY since NOTIFY_RETRIEVE handler returned OK which is
understood by clients as that NOTIFY_REPLY was queued and will be sent
back.

Cap requested size to negotiate max_write to avoid the problem.  This
aligns with the way NOTIFY_RETRIEVE handler works, which already
unconditionally caps requested retrieve size to fuse_conn->max_pages.  This
way it should not hurt NOTIFY_RETRIEVE semantic if we return less data than
was originally requested.

Please see [1] for context where the problem of stuck filesystem was hit
for real, how the situation was traced and for more involving patch that
did not make it into the tree.

[1] https://marc.info/?l=linux-fsdevel&m=155057023600853&w=2
[2] https://github.com/hanwen/go-fuseSigned-off-by: Kirill Smelkov's avatarKirill Smelkov <kirr@nexedi.com>
Cc: Han-Wen Nienhuys <hanwen@google.com>
Cc: Jakob Unterwurzacher <jakobunt@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
      7640682e
    • Kirill Smelkov's avatar
      fuse: allow filesystems to have precise control over data cache · ad2ba64d
      Kirill Smelkov authored 
      On networked filesystems file data can be changed externally.  FUSE
provides notification messages for filesystem to inform kernel that
metadata or data region of a file needs to be invalidated in local page
cache. That provides the basis for filesystem implementations to invalidate
kernel cache explicitly based on observed filesystem-specific events.

FUSE has also "automatic" invalidation mode(*) when the kernel
automatically invalidates data cache of a file if it sees mtime change.  It
also automatically invalidates whole data cache of a file if it sees file
size being changed.

The automatic mode has corresponding capability - FUSE_AUTO_INVAL_DATA.
However, due to probably historical reason, that capability controls only
whether mtime change should be resulting in automatic invalidation or
not. A change in file size always results in invalidating whole data cache
of a file irregardless of whether FUSE_AUTO_INVAL_DATA was negotiated(+).

The filesystem I write[1] represents data arrays stored in networked
database as local files suitable for mmap. It is read-only filesystem -
changes to data are committed externally via database interfaces and the
filesystem only glues data into contiguous file streams suitable for mmap
and traditional array processing. The files are big - starting from
hundreds gigabytes and more. The files change regularly, and frequently by
data being appended to their end. The size of files thus changes
frequently.

If a file was accessed locally and some part of its data got into page
cache, we want that data to stay cached unless there is memory pressure, or
unless corresponding part of the file was actually changed. However current
FUSE behaviour - when it sees file size change - is to invalidate the whole
file. The data cache of the file is thus completely lost even on small size
change, and despite that the filesystem server is careful to accurately
translate database changes into FUSE invalidation messages to kernel.

Let's fix it: if a filesystem, through new FUSE_EXPLICIT_INVAL_DATA
capability, indicates to kernel that it is fully responsible for data cache
invalidation, then the kernel won't invalidate files data cache on size
change and only truncate that cache to new size in case the size decreased.

(*) see 72d0d248 "fuse: add FUSE_AUTO_INVAL_DATA init flag",
eed2179e "fuse: invalidate inode mapping if mtime changes"

(+) in writeback mode the kernel does not invalidate data cache on file
size change, but neither it allows the filesystem to set the size due to
external event (see 8373200b "fuse: Trust kernel i_size only")

[1] https://lab.nexedi.com/kirr/wendelin.core/blob/a50f1d9f/wcfs/wcfs.go#L20Signed-off-by: Kirill Smelkov's avatarKirill Smelkov <kirr@nexedi.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
      ad2ba64d
    • Kirill Smelkov's avatar
      fuse: convert printk -> pr_* · f2294482
      Kirill Smelkov authored 
      Functions, like pr_err, are a more modern variant of printing compared to
printk. They could be used to denoise sources by using needed level in
the print function name, and by automatically inserting per-driver /
function / ... print prefix as defined by pr_fmt macro. pr_* are also
said to be used in Documentation/process/coding-style.rst and more
recent code - for example overlayfs - uses them instead of printk.

Convert CUSE and FUSE to use the new pr_* functions.

CUSE output stays completely unchanged, while FUSE output is amended a
bit for "trying to steal weird page" warning - the second line now comes
also with "fuse:" prefix. I hope it is ok.
Suggested-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Kirill Smelkov's avatarKirill Smelkov <kirr@nexedi.com>
Reviewed-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
      f2294482
    • Liu Bo's avatar
      fuse: honor RLIMIT_FSIZE in fuse_file_fallocate · 0cbade02
      Liu Bo authored 
      fstests generic/228 reported this failure that fuse fallocate does not
honor what 'ulimit -f' has set.

This adds the necessary inode_newsize_ok() check.
Signed-off-by: default avatarLiu Bo <bo.liu@linux.alibaba.com>
Fixes: 05ba1f08 ("fuse: add FALLOCATE operation")
Cc: <stable@vger.kernel.org> # v3.5
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
      0cbade02
    • Miklos Szeredi's avatar
      fuse: fix writepages on 32bit · 9de5be06
      Miklos Szeredi authored 
      Writepage requests were cropped to i_size & 0xffffffff, which meant that
mmaped writes to any file larger than 4G might be silently discarded.

Fix by storing the file size in a properly sized variable (loff_t instead
of size_t).
Reported-by: default avatarAntonio SJ Musumeci <trapexit@spawn.link>
Fixes: 6eaf4782 ("fuse: writepages: crop secondary requests")
Cc: <stable@vger.kernel.org> # v3.13
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
      9de5be06
  3. 21 Apr, 2019 1 commit
  5. 20 Apr, 2019 11 commits
  7. 19 Apr, 2019 23 commits
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