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2020-06-13watch_queue: add gitignore for generated sample programLinus Torvalds1-0/+1
Let's keep "git status" happy and quiet. Fixes: f5b5a164f9a1 ("Add sample notification program") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-19pipe: Add notification lossage handlingDavid Howells1-0/+3
Add handling for loss of notifications by having read() insert a loss-notification message after it has read the pipe buffer that was last in the ring when the loss occurred. Lossage can come about either by running out of notification descriptors or by running out of space in the pipe ring. Signed-off-by: David Howells <dhowells@redhat.com>
2020-05-19pipe: Allow buffers to be marked read-whole-or-error for notificationsDavid Howells1-1/+1
Allow a buffer to be marked such that read() must return the entire buffer in one go or return ENOBUFS. Multiple buffers can be amalgamated into a single read, but a short read will occur if the next "whole" buffer won't fit. This is useful for watch queue notifications to make sure we don't split a notification across multiple reads, especially given that we need to fabricate an overrun record under some circumstances - and that isn't in the buffers. Signed-off-by: David Howells <dhowells@redhat.com>
2020-05-19Add sample notification programDavid Howells2-0/+190
The sample program is run like: ./samples/watch_queue/watch_test and watches "/" for mount changes and the current session keyring for key changes: # keyctl add user a a @s 1035096409 # keyctl unlink 1035096409 @s producing: # ./watch_test read() = 16 NOTIFY[000]: ty=000001 sy=02 i=00000110 KEY 2ffc2e5d change=2[linked] aux=1035096409 read() = 16 NOTIFY[000]: ty=000001 sy=02 i=00000110 KEY 2ffc2e5d change=3[unlinked] aux=1035096409 Other events may be produced, such as with a failing disk: read() = 22 NOTIFY[000]: ty=000003 sy=02 i=00000416 USB 3-7.7 dev-reset e=0 r=0 read() = 24 NOTIFY[000]: ty=000002 sy=06 i=00000418 BLOCK 00800050 e=6[critical medium] s=64000ef8 This corresponds to: blk_update_request: critical medium error, dev sdf, sector 1677725432 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0 in dmesg. Signed-off-by: David Howells <dhowells@redhat.com>