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Fri, 22 Nov 2024 10:58:13 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 0YYNDcVjQGcCKQAAD6G6ig (envelope-from ); Fri, 22 Nov 2024 10:58:13 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id D30A8A08B8; Fri, 22 Nov 2024 11:58:07 +0100 (CET) Date: Fri, 22 Nov 2024 11:58:07 +0100 From: Jan Kara To: Amir Goldstein Cc: Jan Kara , linux-fsdevel@vger.kernel.org, Josef Bacik , brauner@kernel.org, Linus Torvalds , Al Viro , linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 03/19] fsnotify: check if file is actually being watched for pre-content events on open Message-ID: <20241122105807.svnmrwc3db3jqa5s@quack3> References: <20241121112218.8249-1-jack@suse.cz> <20241121112218.8249-4-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Action: no action X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 6C3A6A0007 X-Stat-Signature: 7e4of1ue54t5gja1endrwbrdxf4k6i7z X-Rspam-User: X-HE-Tag: 1732273057-812197 X-HE-Meta: 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 L14RCvHZ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu 21-11-24 17:01:13, Amir Goldstein wrote: > On Thu, Nov 21, 2024 at 12:22 PM Jan Kara wrote: > > > > From: Amir Goldstein > > > > So far, we set FMODE_NONOTIFY_ flags at open time if we know that there > > are no permission event watchers at all on the filesystem, but lack of > > FMODE_NONOTIFY_ flags does not mean that the file is actually watched. > > > > For pre-content events, it is possible to optimize things so that we > > don't bother trying to send pre-content events if file was not watched > > (through sb, mnt, parent or inode itself) on open. Set FMODE_NONOTIFY_ > > flags according to that. > > > > Signed-off-by: Amir Goldstein > > Signed-off-by: Jan Kara > > Link: https://patch.msgid.link/2ddcc9f8d1fde48d085318a6b5a889289d8871d8.1731684329.git.josef@toxicpanda.com > > --- > > fs/notify/fsnotify.c | 27 +++++++++++++++++++++++++-- > > include/linux/fsnotify_backend.h | 3 +++ > > 2 files changed, 28 insertions(+), 2 deletions(-) > > > > diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c > > index 569ec356e4ce..dd1dffd89fd6 100644 > > --- a/fs/notify/fsnotify.c > > +++ b/fs/notify/fsnotify.c > > @@ -193,7 +193,7 @@ static bool fsnotify_event_needs_parent(struct inode *inode, __u32 mnt_mask, > > return mask & marks_mask; > > } > > > > -/* Are there any inode/mount/sb objects that are interested in this event? */ > > +/* Are there any inode/mount/sb objects that watch for these events? */ > > static inline bool fsnotify_object_watched(struct inode *inode, __u32 mnt_mask, > > __u32 mask) > > { > > @@ -632,7 +632,9 @@ EXPORT_SYMBOL_GPL(fsnotify); > > */ > > void file_set_fsnotify_mode(struct file *file) > > { > > - struct super_block *sb = file->f_path.dentry->d_sb; > > + struct dentry *dentry = file->f_path.dentry, *parent; > > + struct super_block *sb = dentry->d_sb; > > + __u32 mnt_mask, p_mask; > > > > /* Is it a file opened by fanotify? */ > > if (FMODE_FSNOTIFY_NONE(file->f_mode)) > > @@ -658,6 +660,27 @@ void file_set_fsnotify_mode(struct file *file) > > file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; > > return; > > } > > This was lost in translation: > > @@ -672,8 +672,10 @@ void file_set_fsnotify_mode(struct file *file) > /* > * If there are permission event watchers but no pre-content event > * watchers, set FMODE_NONOTIFY | FMODE_NONOTIFY_PERM to indicate that. > + * Pre-content events are only reported for regular files and dirs. > */ > - if (likely(!fsnotify_sb_has_priority_watchers(sb, > + if ((!d_is_dir(dentry) && !d_is_reg(dentry)) || > + likely(!fsnotify_sb_has_priority_watchers(sb, > FSNOTIFY_PRIO_PRE_CONTENT))) { > file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; > return; Right. Specifically the (!d_is_dir(dentry) && !d_is_reg(dentry)) got lost, likely when I moved stuff between different commits and then was resolving patch conflicts. I'll add it back. Thanks for finding this! > > + > > + /* > > + * OK, there are some pre-content watchers. Check if anybody can be > > + * watching for pre-content events on *this* file. > > + */ > > + mnt_mask = READ_ONCE(real_mount(file->f_path.mnt)->mnt_fsnotify_mask); > > + if (likely(!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED) && > > + !fsnotify_object_watched(d_inode(dentry), mnt_mask, > > + FSNOTIFY_PRE_CONTENT_EVENTS))) { > > + file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; > > + return; > > + } > > + > > + /* Even parent is not watching for pre-content events on this file? */ > > + parent = dget_parent(dentry); > > + p_mask = fsnotify_inode_watches_children(d_inode(parent)); > > + dput(parent); > > + if (!(p_mask & FSNOTIFY_PRE_CONTENT_EVENTS)) { > > + file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; > > + return; > > + } > > inlining broke the logic and your branch fails the new PRE_ACCESS > test cases of fanotify03 LTP test (now pushed to branch fan_hsm). > > Specifically in the test case that fails, parent is not watching and > inode is watching pre-content and your code gets to the p_mask > test and marks this file as no-pre-content watchers. > > This passes the test: > > @@ -684,17 +686,18 @@ void file_set_fsnotify_mode(struct file *file) > * watching for pre-content events on *this* file. > */ > mnt_mask = READ_ONCE(real_mount(file->f_path.mnt)->mnt_fsnotify_mask); > - if (likely(!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED) && > - !fsnotify_object_watched(d_inode(dentry), mnt_mask, > - FSNOTIFY_PRE_CONTENT_EVENTS))) { > - file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; > + if (unlikely(fsnotify_object_watched(d_inode(dentry), mnt_mask, > + FSNOTIFY_PRE_CONTENT_EVENTS))) { > return; > } > > /* Even parent is not watching for pre-content events on this file? */ > - parent = dget_parent(dentry); > - p_mask = fsnotify_inode_watches_children(d_inode(parent)); > - dput(parent); > + p_mask = 0; > + if (unlikely(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED)) { > + parent = dget_parent(dentry); > + p_mask = fsnotify_inode_watches_children(d_inode(parent)); > + dput(parent); > + } > if (!(p_mask & FSNOTIFY_PRE_CONTENT_EVENTS)) { > file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; > return; Right. I've fixed that up. Thanks! LTP from your fan_hsm branch is now passing so I've re-pushed the current state to my fsnotify_hsm branch. Honza -- Jan Kara SUSE Labs, CR