v2: https://lore.kernel.org/linux-fsdevel/cover.1723144881.git.josef@xxxxxxxxxxxxxx/ v1: https://lore.kernel.org/linux-fsdevel/cover.1721931241.git.josef@xxxxxxxxxxxxxx/ v2->v3: - Fix the pagefault path to do MAY_ACCESS instead, updated the perm handler to emit PRE_ACCESS in this case, so we can avoid the extraneous perm event as per Amir's suggestion. - Reworked the exported helper so the per-filesystem changes are much smaller, per Amir's suggestion. - Fixed the screwup for DAX writes per Chinner's suggestion. - Added Christian's reviewed-by's where appropriate. v1->v2: - reworked the page fault logic based on Jan's suggestion and turned it into a helper. - Added 3 patches per-fs where we need to call the fsnotify helper from their ->fault handlers. - Disabled readahead in the case that there's a pre-content watch in place. - Disabled huge faults when there's a pre-content watch in place (entirely because it's untested, theoretically it should be straightforward to do). - Updated the command numbers. - Addressed the random spelling/grammer mistakes that Jan pointed out. - Addressed the other random nits from Jan. --- Original email --- Hello, These are the patches for the bare bones pre-content fanotify support. The majority of this work is Amir's, my contribution to this has solely been around adding the page fault hooks, testing and validating everything. I'm sending it because Amir is traveling a bunch, and I touched it last so I'm going to take all the hate and he can take all the credit. There is a PoC that I've been using to validate this work, you can find the git repo here https://github.com/josefbacik/remote-fetch This consists of 3 different tools. 1. populate. This just creates all the stub files in the directory from the source directory. Just run ./populate ~/linux ~/hsm-linux and it'll recursively create all of the stub files and directories. 2. remote-fetch. This is the actual PoC, you just point it at the source and destination directory and then you can do whatever. ./remote-fetch ~/linux ~/hsm-linux. 3. mmap-validate. This was to validate the pagefault thing, this is likely what will be turned into the selftest with remote-fetch. It creates a file and then you can validate the file matches the right pattern with both normal reads and mmap. Normally I do something like ./mmap-validate create ~/src/foo ./populate ~/src ~/dst ./rmeote-fetch ~/src ~/dst ./mmap-validate validate ~/dst/foo I did a bunch of testing, I also got some performance numbers. I copied a kernel tree, and then did remote-fetch, and then make -j4 Normal real 9m49.709s user 28m11.372s sys 4m57.304s HSM real 10m6.454s user 29m10.517s sys 5m2.617s So ~17 seconds more to build with HSM. I then did a make mrproper on both trees to see the size [root@fedora ~]# du -hs /src/linux 1.6G /src/linux [root@fedora ~]# du -hs dst 125M dst This mirrors the sort of savings we've seen in production. Meta has had these patches (minus the page fault patch) deployed in production for almost a year with our own utility for doing on-demand package fetching. The savings from this has been pretty significant. The page-fault hooks are necessary for the last thing we need, which is on-demand range fetching of executables. Some of our binaries are several gigs large, having the ability to remote fetch them on demand is a huge win for us not only with space savings, but with startup time of containers. There will be tests for this going into LTP once we're satisfied with the patches and they're on their way upstream. Thanks, Josef Amir Goldstein (8): fsnotify: introduce pre-content permission event fsnotify: generate pre-content permission event on open fanotify: introduce FAN_PRE_ACCESS permission event fanotify: introduce FAN_PRE_MODIFY permission event fanotify: pass optional file access range in pre-content event fanotify: rename a misnamed constant fanotify: report file range info with pre-content events fanotify: allow to set errno in FAN_DENY permission response Josef Bacik (8): fanotify: don't skip extra event info if no info_mode is set fanotify: add a helper to check for pre content events fanotify: disable readahead if we have pre-content watches mm: don't allow huge faults for files with pre content watches fsnotify: generate pre-content permission event on page fault bcachefs: add pre-content fsnotify hook to fault gfs2: add pre-content fsnotify hook to fault xfs: add pre-content fsnotify hook for write faults fs/bcachefs/fs-io-pagecache.c | 4 + fs/gfs2/file.c | 4 + fs/namei.c | 9 ++ fs/notify/fanotify/fanotify.c | 32 +++++-- fs/notify/fanotify/fanotify.h | 20 +++++ fs/notify/fanotify/fanotify_user.c | 116 ++++++++++++++++++++----- fs/notify/fsnotify.c | 14 ++- fs/xfs/xfs_file.c | 9 +- include/linux/fanotify.h | 20 +++-- include/linux/fsnotify.h | 54 ++++++++++-- include/linux/fsnotify_backend.h | 59 ++++++++++++- include/linux/mm.h | 1 + include/uapi/linux/fanotify.h | 17 ++++ mm/filemap.c | 134 +++++++++++++++++++++++++++-- mm/memory.c | 22 +++++ mm/readahead.c | 13 +++ security/selinux/hooks.c | 3 +- 17 files changed, 478 insertions(+), 53 deletions(-) -- 2.43.0
