On Tue, May 19, 2015 at 05:12:35AM -0400, Krutika Dhananjay wrote: > Hi, > > The following patch fixes an issue with readdir(p) in shard xlator: http://review.gluster.org/#/c/10809/ whose details can be found in the commit message. > > One side effect of this is that from shard xlator, the size of the dirents list returned to the translators above it could be greater than the > requested size in the wind path (thanks to Pranith for pointing this out during the review of this patch), with the worst-case scenario returning (2 * requested_size) worth of entries. > For example, if fuse requests readdirp with 128k as the size, in the worst case, 256k worth of entries could be unwound in return. > How important is it to strictly adhere to this size limit in each iteration of readdir(p)? And what are the repercussions of such behavior? > > Note: > I tried my hand at simulating this issue on my volume but I have so far been unsuccessful at hitting this test case. > Creating large number of files on the root of a sharded volume, triggering readdirp on it until ".shard" becomes the last entry read in a given iteration, winding the next > readdirp from shard xlator, and then concatenating the results of two readdirps into one is proving to be an exercise in futility. > Therefore, I am asking this question here to know what could happen "in theory" in such situations. How about modifying xlators/mount/fuse/src/fuse-bridge.c and increasing the size of the readdir(p) argument there? The FUSE kernel side would not know about the increased size, but the other xlators would request a bigger size in subsequent readdir(p) FOPs. I suspect that the additional dentries in readdir(p) get dropped, and the next getdents() call from the kernel continues are the offset of the readdir(p) of the last returned dentry. Niels _______________________________________________ Gluster-devel mailing list Gluster-devel@xxxxxxxxxxx http://www.gluster.org/mailman/listinfo/gluster-devel
