From: Maxim P. <MPa...@pa...> - 2013-06-13 08:17:34
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Changing size of a file on server and local update (fuse_write_update_size) should be always protected by inode->i_mutex. Otherwise a race like this is possible: 1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE). fuse_file_fallocate() sends FUSE_FALLOCATE request to the server. 2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr() sends shrinking FUSE_SETATTR request to the server and updates local i_size by i_size_write(inode, outarg.attr.size). 3. Process 'A' resumes execution of fuse_file_fallocate() and calls fuse_write_update_size(inode, offset + length). But 'offset + length' was obsoleted by ftruncate from previous step. Changed in v2 (thanks Brian and Anand for suggestions): - made relation between mutex_lock() and fuse_set_nowrite(inode) more explicit and clear. - updated patch description to use ftruncate(2) in example Signed-off-by: Maxim V. Patlasov <MPa...@pa...> --- fs/fuse/file.c | 12 ++++++++---- 1 files changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index e570081..35f2810 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2470,13 +2470,16 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, .mode = mode }; int err; + bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) || + (mode & FALLOC_FL_PUNCH_HOLE); if (fc->no_fallocate) return -EOPNOTSUPP; - if (mode & FALLOC_FL_PUNCH_HOLE) { + if (lock_inode) { mutex_lock(&inode->i_mutex); - fuse_set_nowrite(inode); + if (mode & FALLOC_FL_PUNCH_HOLE) + fuse_set_nowrite(inode); } req = fuse_get_req_nopages(fc); @@ -2511,8 +2514,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, fuse_invalidate_attr(inode); out: - if (mode & FALLOC_FL_PUNCH_HOLE) { - fuse_release_nowrite(inode); + if (lock_inode) { + if (mode & FALLOC_FL_PUNCH_HOLE) + fuse_release_nowrite(inode); mutex_unlock(&inode->i_mutex); } |
From: Brian F. <bf...@re...> - 2013-06-13 11:49:08
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On 06/13/2013 04:16 AM, Maxim Patlasov wrote: > Changing size of a file on server and local update (fuse_write_update_size) > should be always protected by inode->i_mutex. Otherwise a race like this is > possible: > > 1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE). > fuse_file_fallocate() sends FUSE_FALLOCATE request to the server. > 2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr() > sends shrinking FUSE_SETATTR request to the server and updates local i_size > by i_size_write(inode, outarg.attr.size). > 3. Process 'A' resumes execution of fuse_file_fallocate() and calls > fuse_write_update_size(inode, offset + length). But 'offset + length' was > obsoleted by ftruncate from previous step. > > Changed in v2 (thanks Brian and Anand for suggestions): > - made relation between mutex_lock() and fuse_set_nowrite(inode) more > explicit and clear. > - updated patch description to use ftruncate(2) in example > > Signed-off-by: Maxim V. Patlasov <MPa...@pa...> > --- Makes more sense and I like the cleanup... thanks. Reviewed-by: Brian Foster <bf...@re...> > fs/fuse/file.c | 12 ++++++++---- > 1 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > index e570081..35f2810 100644 > --- a/fs/fuse/file.c > +++ b/fs/fuse/file.c > @@ -2470,13 +2470,16 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, > .mode = mode > }; > int err; > + bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) || > + (mode & FALLOC_FL_PUNCH_HOLE); > > if (fc->no_fallocate) > return -EOPNOTSUPP; > > - if (mode & FALLOC_FL_PUNCH_HOLE) { > + if (lock_inode) { > mutex_lock(&inode->i_mutex); > - fuse_set_nowrite(inode); > + if (mode & FALLOC_FL_PUNCH_HOLE) > + fuse_set_nowrite(inode); > } > > req = fuse_get_req_nopages(fc); > @@ -2511,8 +2514,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, > fuse_invalidate_attr(inode); > > out: > - if (mode & FALLOC_FL_PUNCH_HOLE) { > - fuse_release_nowrite(inode); > + if (lock_inode) { > + if (mode & FALLOC_FL_PUNCH_HOLE) > + fuse_release_nowrite(inode); > mutex_unlock(&inode->i_mutex); > } > > |
From: Miklos S. <mi...@sz...> - 2013-06-17 23:49:34
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On Thu, Jun 13, 2013 at 1:46 PM, Brian Foster <bf...@re...> wrote: > On 06/13/2013 04:16 AM, Maxim Patlasov wrote: >> Changing size of a file on server and local update (fuse_write_update_size) >> should be always protected by inode->i_mutex. Otherwise a race like this is >> possible: >> >> 1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE). >> fuse_file_fallocate() sends FUSE_FALLOCATE request to the server. >> 2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr() >> sends shrinking FUSE_SETATTR request to the server and updates local i_size >> by i_size_write(inode, outarg.attr.size). >> 3. Process 'A' resumes execution of fuse_file_fallocate() and calls >> fuse_write_update_size(inode, offset + length). But 'offset + length' was >> obsoleted by ftruncate from previous step. >> >> Changed in v2 (thanks Brian and Anand for suggestions): >> - made relation between mutex_lock() and fuse_set_nowrite(inode) more >> explicit and clear. >> - updated patch description to use ftruncate(2) in example >> >> Signed-off-by: Maxim V. Patlasov <MPa...@pa...> Thanks, applied. Miklos |